sedimentary
Chert (Yellow Jasper variant)
Microcrystalline Quartz (SiO2)
Hardness: 6.5–7 on Mohs scale; Color: Dull yellow to tan; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6–2.7
- Hardness
- 6
- Color
- Dull yellow to tan
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5–7 on Mohs scale; Color: Dull yellow to tan; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6–2.7
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. This specimen is a water-worn river pebble, likely shaped over thousands of years.
Uses & applications
Historically used for stone tools/arrowheads. Modern uses include jewelry (if polished), landscaping gravel, and as a raw material for silicon production.
Geological facts
Yellow chert gets its color from iron oxide (limonite) inclusions. Due to its fracture patterns, it was one of the most important materials for early human technology, categorized as 'lithic' archaeological material.
Field identification & locations
Identify in the field by its smooth, 'heart-shaped' or rounded water-worn texture and its inability to be scratched by a steel pocket knife. Found commonly in riverbeds and glacial tills.
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